1. Field of the Invention
The present invention relates generally to self-propelled irrigation systems and, in particular, to a drive unit for a tower of a self-propelled irrigation system that provides improved traction and flotation as the sprinkler traverses a field.
2. Description of the Related Art
Self-propelled irrigation systems are used to provide water for agricultural purposes in arid regions. Typically, such systems include a series of spaced drive towers connected by truss sections that support an elongated water distribution pipeline between the towers. In center pivot systems, the water distribution pipe extends radially from a central pivot connected to a water supply. In linear move irrigation systems, the water distribution pipe extends laterally from a canal feed or hose drag system that provides the water supply.
Water passing through the distribution pipeline is forced out through a number of sprinkler heads, spray guns, drop nozzles, or the like spaced along the length of the pipe. Each drive tower in the system is supported on wheels or other structures that are driven at slow speeds to move the tower in a circular path about the central pivot, or a linear path in the case of linear move systems, to thereby irrigate a large tract of land.
Conventional drive towers for self-propelled irrigation systems are each supported by an elongated base beam that extends transverse to the water pipeline with a drive wheel at each end of the base beam. The weight of the drive tower and the corresponding part of the water pipeline is approximately evenly distributed between the two drive wheels. However, in difficult terrain these two-wheeled drive towers sometimes become stuck or leave deep ruts in the field, which are undesirable.
There have been many attempts in the prior art to improve the flotation and traction of conventional drive towers for self-propelled irrigation systems. For example, there have been three-wheeled drive towers in which all three wheel assemblies are mounted to a rigid base beam. However, these drive towers do not maintain a constant weight distribution among the three wheels and often have one wheel come off the ground when the system traverses uneven terrain.
Additional attempts to improve drive towers are described in U.S. Pat. No. 6,131,833 issued to Chapman (tracked drive tower), and U.S. Pat. No. 7,229,032 issued to Christensen et al. (four-wheeled drive tower). However, these attempted solutions have been complex and expensive to implement and appear to have had only limited acceptance in the marketplace.
There is a need in the industry for an improved drive tower for self-propelled irrigation systems to allow the irrigation systems to traverse difficult and uneven terrain more easily.